1. Field of the Invention
The present invention is related to wireless tracking systems and methods. More specifically, the present invention relates to a system and method for determining if a tracking tag has been removed from an asset.
2. Description of the Related Art
The ability to quickly determine the location of objects located within a facility is becoming a necessity of life. To the uninformed observer, the placement of transponders, also known as tags, on numerous non-stationary objects whether in an office or home would appear to be an unnecessary use of resources. However, the uninformed observer fails to appreciate the complexity of modern life and the desire for efficiency, whether at the office or home.
For example, in a typical hospital there are numerous shifts of employees utilizing the same equipment. When a new shift arrives the ability to quickly locate medical equipment not only results in a more efficient use of resources, but also can result in averting a medical emergency. Thus, the tracking of medical equipment in a hospital is becoming a standard practice.
The tracking of objects in other facilities is rapidly becoming a means of achieving greater efficiency. A typical radio frequency identification system includes at least multiple tagged objects, each of which transmits a signal, multiple receivers for receiving the transmissions from the tagged objects, and a processing means for analyzing the transmissions to determine the locations of the tagged objects within a predetermined environment. One exemplary method triangulates the strongest received signals to determine the location of a tagged object. This method is based on the assumption that the receivers with the strongest received signals are the ones located closest to the tagged object. However, such an assumption is sometimes erroneous due to common environmental obstacles. Multipath effects can result in a further located receiver having a stronger signal from a tagged object than a more proximate receiver to the tagged object, which result in a mistaken location determination.
Yashina, U.S. Pat. No. 5,068,643, for a Burglarproof Device, discloses a device that includes a vibration sensor and an optical sensor. When the vibration sensor is activated, by vibration, a signal is sent to the optical sensor to determine the level of ambient light from relative brightness to relative darkness. If the ambient level is too dark, an alarm circuit is activated on the device to indicate that the goods to which the device is attached has been placed under or in a thief's clothing.
Watters, et al., U.S. Pat. No. 6,806,808, for a Wireless Event-Recording Device With Identification Codes, discloses a passive transponder that has a sensor for detecting a physical or chemical event or state without using a power source of its own.
Glick, et al., U.S. Pat. No. 7,002,473, for a Loss Prevention Device, discloses placing a RFID tag on an article and periodically interrogating each RFID tag to determine if the tag is still within a predetermined zone.
Clucas, U.S. Pat. No. 7,042,359, for a Method And Apparatus To Detect A Plurality Of Security Tags discloses an electronic article surveillance system which includes a multitude of expensive RFID tags attached to expensive goods and a multitude of inexpensive RFID tags attached to inexpensive goods, and means to distinguish between the types of tags.
Although the prior art has provided numerous solutions to prevent the theft of goods, the prior art has yet to resolve tag removal issues associated with location asset tracking. Further, the prior art has failed to recognize the problems associated with wireless location asset tracking.